1. Field of the Invention
The present invention relates to a method for manufacturing a paper-based container, the devices for its implementation and the containers thus obtained.
2. Description of Background and Material Information
Containers generally designed for containing liquids are known, FIGS. 1 and 2 illustrating an example having a rectangular front surface 1 and a rectangular rear surface 2, having the same width and height, and a bottom 3 formed from a rectangular sheet having the same width and a substantially lower height than the front 1 and rear 2 surfaces, and folded in half along its width to form a bellows. The complex film constituting the front 1 and rear 2 surfaces has, on the outside, a film made of a plastic material that is rendered semi-rigid by using it in a more substantial thickness than strictly required and, on the inside, a glued film that is adapted for welding at a substantially lower temperature than the fusion temperature of the outside film. On the contrary, the complex film composing the bellows is very flexible but has a similar structure with an outside film supporting a glued film for welding. The front 1 and rear 2 surfaces are bound together by the welding of their lateral parts 4 either directly at their upper portion, or indirectly at their lower portion via the bottom 3 forming the bellows. The edges 14 of the bellows forming the bottom 3 laterally have, in the width of the lateral welds 4, cutouts 5 (FIG. 5) that correspond to one another such that the front 1 and rear 2 surfaces come into contact directly at the level of the bottom 3 and are welded together so as to laterally block the opening of the bellows formed by the bottom 3. Each side of the bellows of the bottom 3 is furthermore bound to the front 1 and rear 2 surfaces facing it respectively, in the middle part located between the lateral parts 4 on the surface of a binding zone 13 extending from the support base 6 to a "U"-shaped curve 7 that starts at the upper fold 8 of the bottom 3 forming the bellows, at the level of the left lateral part 4, to end back at the upper fold 8 of the bottom 3 forming the bellows, but at the level of the right lateral part 4, the middle part 9 of the curve 7 being a few millimeters away from the support base 6. When such a small bag is unfolded, the front 1 and rear 2 surfaces (FIG. 2) are spaced from each other by bending in the shape of a half cylinder having vertical generatrices and a cross-section predetermined by the previously described "U"-shaped curve 7 limiting the binding zone 13 of the bottom 3 forming the bellows which is bound to the front 1 and rear 2 surfaces. The bottom 3 forming the bellows is unfolded until its free part 10 is stretched, which provides a maximum spacing in the middle part 9 of the curve 7 which is also the middle part of the front 1 and rear 2 surfaces. In this zone, the free part 10 of the bottom 3 is near the support base 6, and the spacing of the front 1 and rear 2 surfaces is gradually reduced as it nears the edges, and the free part 10 of the bottom 3 progressively rises to the level of the fold 12 of the bottom 3 where the front 1 and rear 2 surfaces come together to be welded. The support base 6 is formed by the base of the front 1 and rear 2 surfaces, welded to the walls of the bottom 3 forming the bellows, which provides a sufficient rigidity so that the container stands upright. This container is generally filled, especially with a liquid, and the front 1 and rear 2 surfaces are welded together at their top so as to seal the container. The welding of this container's inside film is achieved by a high frequency radiation to which the outside film is not susceptible.